Induction heating device for successive barlike members

ABSTRACT

An improvement in an induction heating apparatus for heating a succession of abutting barlike members which apparatus includes an elongated multiturn induction heating coil with an elongated internal passageway through which the members pass, a power supply means for energizing the coil with an alternating current, and means extending between the entrance and exit of the passageway for guiding members through the passageway on a selected path. The improvement comprises forming the guide means with an elongated element with a contoured portion between the entrance and exit of the passageway which contoured portion creates a gradual offset in a selected transverse direction to the path so that the members do not pass through the coil with their abutting ends in full contact with each other.

United States Patent [72] Inventor Norbert R. Balzer 3,083,285 3/1963 Haimbough et al 219/10.69 P i 3,301,990 1/1967 Neal 2l9/10.69 X 1 1 pp $3 968 FOREIGN PATENTS 221 Filed ,1 [45] Patented Oct. 12, 1971 1,186,569 2/1965 Germany I. 219/10.69 [73] Assignee Granted to US. Atomic Energy Primary Examiner-loseph Tmhe Commission under the provisions of 42 Assistant Bender s 2132 Attorney-Roland A. Anderson 541 INDUCTION HEATING DEVICE FOR SUCCESSIVE ABSTRACT 'f heamg BARLIKE MEMBERS paratus for heatmg a successlon of abutting barlIke members 10 Claims 4Drawing Figs whIch apparatus Includes an elongated multItum Induction heating coil with an elongated internal passageway through [52] 11.8. C1 219/10.69, which'the members pass a power supply means for energizing 2 1 the coil with an alternating current, and means extending [51] Int. Cl H051) 5/00, between the entrance and exit of the passageway for guiding members through the passageway on a selected path. The im- [50] Field Of Search p 'ovement comprises forming the guide means with an eion. gated element with a contoured portion between the entrance [56] Rekrences and exit of the passageway which contoured portion creates a UNITED STATES PATENTS gradual offset in a selected transverse direction to the path so 3,051,811 8/1962 Koesling 219/ 10.69 X tha t me ber do n pas hroug t o t their 3,051,812 8/ 1962 Gschwender 219/ 10.69 abutting ends in full contact with each other.

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1 ewe e meme weep e ewe INDUCTION HEATING DEVICE FOR SUCCESSIVE IIARLIKE MEMBERS This invention relates to the art of induction heating, and more particularly to an improved apparatus for inductively heating a succession of abutting barlike workpieces or members as they pass through a solenoid-type induction heating coil.

The invention is particularly applicable for heating a succession of uranium billets for grain orientation of the billets, and it will be described with particular reference thereto; however, it should be appreciated that the invention has much broader applications and may be used in other instances where a succession of workpieces are heated by passing them in succession through an induction heating coil, such as in hardening and tempering successive billets.

When a uranium billet is to be heat treated for grain orientation, it is heated to an appropriate'temperature by a heating device. The heating temperature should progress from room temperature to about l400 F. The temperature must be uniform over the complete length of the billet to provide uniform grain orientation. When other billets are heated to a hardening temperature or a tempering temperature, this same requirement of uniformity over the total length of the billet is also experienced. In addition to a lesser extent this is a requirement for heating successive billets to be forged. A common practice for such heating operations is to provide an elongated multiturn induction heating coil through which a succession of billets can be passed. As one relatively cold billet is forced into one end of the coil, a heated billet is automatically forced out the other end. This type of mechanism has proven quite satisfactory; however, one difi'lculty has been experienced with this particular arrangement.

An induction heating coil for heating a succession of billets generally includes two spaced rods for guiding the billets through the coil passageway. When a cold billet is pushed into the passageway to eject the heated billet, the power to the coil may be on or off. If the power is off, the coil is thereafter energized to raise the temperature of the billets within the passageway. The guide rails are straight; therefore, the flat ends of the adjacent billets are in direct heat transfer contact. Consequently, the leading edge of the cold billet contacts a previously heated billet. This causes a transfer of heat energy to the cold billet before it is actually heated by the coil so the back end of the heated coil is cooled while the front end of the unheated coil is heated. This causes a differential in temperature along the length of each billet. This differential is maintained over the complete heating cycle since the front billet is always at a temperature below the rear billet. This differential in heat along the length of the billet is not conducive to uniform heat treatment of the billet. In the past, this heat differential could be overcome by holding the billets for a prolonged time to allow stabilization; however, the obvious deficiency of this particular arrangement is apparent. Also, it decreased the efficiency of the heating operation. 7

The present invention is directed toward an improved induction heating device which overcomes the disadvantages of the device as discussed above by including an arrangement which will eliminate the direct heat transfer between adjacent billets being pushed through a multiturn induction heating coil.

In accordance with the present invention, there is provided an improvement in an induction heating apparatus for heating a succession of barlike workpieces which apparatus includes an elongated multiturn induction heating coil with an elongated intemal passageway through which the workpiece is passed, wherein the passageway has an entrance and an exit, and means extending between the entrance and exit of the passageway for guiding the workpieces through the passageway. This improvement includes modifying the guide means so that they have a central contoured portion which causes the workpieces to travel in an arcuate path through the coil. This arcuate path prevents abutting contact between adjacent flat surfaces so that heat transfer is difficult between adjacent billets. In accordance with the preferred embodiment of the invention, the guide rails extending through the induc- I tion heating coils are arcuately shaped to create the arcuate path of movement of the successive workpieces through the induction heating coil.

The primary object of the present invention is the provision of an induction heating apparatus including an elongated coil for heating a succession of abutting barlike elements which apparatus includes means for limiting the contact between adjacent workpieces as they pass through the coil.

Another object of the present invention is the provision of an induction heating apparatus including an elongated coil for heating a succession of abutting barlike elements which apparatus includes means for passing the workpieces through the coil in an arcuate path.

Still another object of the present invention is the provision of an induction heating apparatus including an elongated coil for heating a succession of abutting barlike elements which apparatus includes contoured guide rails extending through the coil to cause the workpieces to move in a generally arcuate path through the coil.

These and other objects and advantages will become apparent from the following description used to illustrate the preferred embodiment of the present invention as read in connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view showing, somewhat schematically, the preferred embodiment of the present invention;

FIG. 2 is a schematic view illustrating an operating charac teristic of the prior art;

FIG. 3 is a schematic view, similar to FIG. 2, showing an operating characteristic of the preferred embodiment of the present invention; and,

FIG. 4 is a cross-sectional view taken generally along line 4-4 of FIG. 1.

Referring now to the drawings, where the showings are for the purpose of illustrating a preferred embodiment of the invention only and not for the purpose of limiting same, FIGS. I and 4 show induction heating apparatus A for heating a succession of workpieces B, the workpieces are illustrated as cylindrical forging billets having a diameter b and designated B1, B2, B3 and B4. A mechanism, schematically represented as a cylinder C having a rod I0 is used to push successive billets through the apparatus A. When a new billet is introduced, a heated billet is pushed from the apparatus.

Although the apparatus A could take a variety of structural forms, the illustrated embodiment of the invention includes a multiturn coil 20 having an internal coolant passage 22 and spaced leads 24, 26. A power supply, schematically represented as generator 30, is connected across leads 24, 26 for the purpose of producing an alternating current through the coil 20. In accordance with standard practice, a power factor correcting capacitor 32 is also connected across the leads 24, 26 for the purpose of maintaining, as close as possible, a unity power factor for the heating installation. As illustrated, coil 20 is encapsulated within a casing 40 having an internal workpiece receiving passageway 42 contoured to generally match the outer dimensions of the billets B. Since the billets are cylindrical, passageway 42 is cylindrical and has a diameter a which is substantially larger than the diameter b of the billets. Consequently, the billets may pass through the passageway 42 without contacting the inner surface of the passageway. It is appreciated that various contours can be provided for the passageway; however, the passageway generally matches the contour of the billets. In addition, the coil generally has a cross section which corresponds with the cross section of the billets so that a relatively uniform magnetic coupling is created between the coil and the billets as they pass through the apparatus A. Rails 50, 52 extend from the left-hand entrance of the passageway 42 to the right-hand exit of this passageway for guiding the billets as they travel therethrough.

As so far explained, the apparatus A does not differ substantially from prior induction heating apparatus. The generator 30 energizes coil 20 and heats the four billets within passageway 42. Billet B4 is heated to the final temperature for grain orientation which may be in the general range of 1400 F. Each of the billets to the left has a progressively lower temperature. Assuming that the final temperature is in the neighborhood of M F., billet Bl would have an average temperature in the general range of 350 F., billet B2 would have an average temperature in the general range of 700 F., and billet B3 would have an average temperature in -the general range of 1050 F. This is assuming general uniform incremental temperature rises in the various billets which is generally accomplished during the heating cycle. After the heating cycle has been completed, generator 30 is deenergized and cylinder C pushes another billet into the passageway 42. This automatically ejects the heated billet B4. This process is repeated to heat progressively successive billets introduced into the passageway 42 of apparatus A.

Referring now to FIG. 2, the operation of apparatus A, as so far explained, is graphically illustrated. Billet B2 has a forward end 60 and a rear end 62. In a like manner, billet B3 has a forward end 64 and a rear end 66. As previously mentioned, billet B2 has an average temperature in the general range of 700 F. whereas billet B3 has an average temperature in the general range of 1050 F. In previous induction heating apparatus, the billets were in abutting relationship with the complete surfaces at adjacent ends of the billets being in direct contact, as shown in FIG. 2. This caused the heat transfer between the adjacent billets which, in turn, caused a heating pattern 70, 72 in the adjacent billets. Pattern 70 represents a decrease in temperature adjacent end 56 and pattern 72 indicates an increase in temperature adjacent end 60. Consequently, in accordance with the prior art, the forward end of the billet was heated to a temperature substantially greater than the rear end. This nonuniformity in heating was not desirable and not conducive to efficient grain orientation.

In accordance with the present invention, the apparatus A is provided with a means for controlling the path 80 followed by the billets as they pass through the passageway 42. In accordance with the preferred embodiment of the invention, the path 80 is arcuate and is created by forming a bow in the central portion of rails 50, 52. This bow has a maximum distance c which is substantially less than the difference between dimensions a and b. By providing an arcuate path 80, spaces 82, 84 and 86 are created between adjacent billets. The billets are not in surface to surface contact; therefore, only a relatively small heat transfer pattern 90 is created between adjacent billets, as shown in FIG. 3. It is obvious that this heat transfer pattern is relatively small and would have a minor effect upon the heating of the adjacent billets.

During a test run on prior art apparatus, the trailing or rear end of each billet had a temperature drop of 48 F. By creating a bow of about 0.4 inches (distance c) in rails having a length of 38 inches (dimension 1) the differential for the rear end of a billet was reduced to F. This is a substantial reduction in the temperature differential at the trailing end of a billet and creates a substantially more uniform heating for the billet. The ratio of In: in this example was approximately 100:1. It is appreciated that variations can be made in this ratio to accomplish varying degrees of temperature differentials.

In accordance with the preferred embodiment of the present invention, the arcuate path 80 is in a vertical plane; however, it could be in a horizontal plane or various planes I therebetween. In addition, the bow could be in a downward direction, as well as in an upward direction. It is also appreciated that it may be possible to create a generally arcuate path through the passage 42 by progressively enlarging and then contracting the spacing between the rails 50, 52 as the rails extend through the passage 42 from the entrance to the exit. Consequently, the billets would gradually move downwardly as the rail spacing increases and then move gradually upwardly as the spacing again decreases. It is appreciated that other similar modifications can be used to accomplish the nonflat contact between the ends of adjacent billets moving through the passageway 42.

Having thus described my invention, I claim: 1. In an induction heating apparatus for heating a succession of abutting barlike workpieces, said apparatus including an elongated multitum induction heating coil with an elongated intemal passageway through which said workpieces pass, said passageway having an entrance and an exit and a length substantially greater than twice the length of said workpieces, and means extending between said entrance and said exit for guiding said workpieces through said passageway on a selected path, the improvement comprising: said guide means including an elongated element with a contoured portion between said entrance and said exit, said contoured portion creating a gradual offset in a selected transverse direction to said path, said passageway has a dimension 0 in said selected direction, said workpieces having a dimension b in said selected transverse direction, a being larger than b, and said offset having a maximum distance 0 in said selected transverse direction, with c being less than a-b.

2. The improvement as defined in claim 1 wherein said offset is in a generally vertical direction.

3. The improvement as defined in claim 2 wherein said contoured portion is generally arcuate.

4. The improvement as defined in claim 3 wherein said contoured portion extends from adjacent said entrance to adjacent said exit.

5. The improvement as defined in claim I wherein said contoured portion is generally arcuate.

6. The improvement as defined in claim 1 wherein the ratio of the length of said passageway to the distance 0 is in the general range of :l. Y

7. The improvement as defined in claim 1 wherein said maximum distance 0 is located generally midway between said entrance and said exit.

8. The improvement as defined in claim 1 wherein said guide means includes two spaced, generally parallel rails.

9. In an induction heating apparatus for heating a succession of abutting barlike workpieces with longitudinal axes, said apparatus including an elongated multiturn induction heating coil with an elongated internal passageway through which said workpieces pass, said passageway having an entrance and an exit and a length substantially greater than twice the length of said workpieces, and means extending between said entrance and said exit for guiding said workpieces through said passageway on a selected path, the improvement comprising: said guide means including position-controlling means for causing said workpieces to pass generally coaxially through said passageway in a generally arcuate path.

10. The improvement as defined in claim 9 wherein said position-controlling means includes two spaced rails with contours for causing said arcuate path. 

1. In an induction heating apparatus for heating a succession of abutting barlike workpieces, said apparatus including an elongated multiturn induction heating coil with an elongated internal passageway through which said workpieces pass, said passageway having an entrance and an exit and a length substantially greater than twice the length of said workpieces, and means extending between said entrance and said exit for guiding said workpieces through said passageway on a selected path, the improvement comprising: said guide means including an elongated element with a contoured portion between said entrance and said exit, said contoured portion creating a gradual offset in a selected transverse direction to said path, said passageway has a dimension a in said selected direction, said workpieces having a dimension b in said selected transverse direction, a being larger than b, and said offset having a maximum distance c in said selected transverse direction, with c being less than ab.
 2. The improvement as defined in claim 1 wherein said offset is in a generally vertical direction.
 3. The improvement as defined in claim 2 wherein said contoured portion is generally arcuate.
 4. The improvement as defined in claim 3 wherein said contoured portion extends from adjacent said entrance to adjacent said exit.
 5. The improvement as defined in claim 1 wherein said contoured portion is generally arcuate.
 6. The improvement as defined in claim 1 wherein the ratio of the length of said pAssageway to the distance c is in the general range of 100:l.
 7. The improvement as defined in claim 1 wherein said maximum distance c is located generally midway between said entrance and said exit.
 8. The improvement as defined in claim 1 wherein said guide means includes two spaced, generally parallel rails.
 9. In an induction heating apparatus for heating a succession of abutting barlike workpieces with longitudinal axes, said apparatus including an elongated multiturn induction heating coil with an elongated internal passageway through which said workpieces pass, said passageway having an entrance and an exit and a length substantially greater than twice the length of said workpieces, and means extending between said entrance and said exit for guiding said workpieces through said passageway on a selected path, the improvement comprising: said guide means including position-controlling means for causing said workpieces to pass generally coaxially through said passageway in a generally arcuate path.
 10. The improvement as defined in claim 9 wherein said position-controlling means includes two spaced rails with contours for causing said arcuate path. 